Medical Physics 2.0. Ultrasound 2.0. N. J. Hangiandreou, Ph.D. 1 P. L. Carson, Ph.D. 2 Z. F. Lu, Ph.D. 3. Mayo Clinic 2. University of Michigan 3

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1 Medical Physics 2.0 Ultrasound 2.0 N. J. Hangiandreou, Ph.D. 1 P. L. Carson, Ph.D. 2 Z. F. Lu, Ph.D. 3 1 Mayo Clinic 2 University of Michigan 3 University of Chicago 2013 MFMER slide-1

2 Overview Ultrasound Perspectives (Paul Carson, PhD) Ultrasound 1.0 (Zheng Feng Lu, PhD) Ultrasound 2.0: How will clinical medical physics support future ultrasound practices? Performance testing Optimization of image quality and exam protocols Clinical innovation Education of physicians, sonographers, residents, medical students, patients Clinical implementation 2013 MFMER slide-2

3 Role of ultrasound in future clinical imaging practices Strengths of ultrasound: image quality, Doppler modes, real-time, portable, safety record, low cost Very wide range of clinical applications adjunct to physical exam, vascular access for interventional radiology procedures, screening, primary diagnosis, guidance of biopsy & fluid aspiration, guidance of ablation (e.g. RF, ETOH), thermal ablation (MRgFUS, HIFU), facilitate soft tissue healing, targeted drug delivery Philips Healthcare 2013 MFMER slide-3

4 Role of ultrasound in future clinical imaging practices Who is using ultrasound? Radiology, Cardiology, Anesthesiology, Obstetrics & Gynecology, Urology, Gastroenterology & Hepatology, Hospital Internal Medicine, The future Continued expansion in clinical applications and exam volumes is expected Increased diversification in user base? 2013 MFMER slide-4

5 Ultrasound Perspectives PL Carson, PhD 1. Perspectives from the past and present 1. Innovations in newer current medical ultrasound systems 2. Physics successes and failures 2. A perspective, from the more distant future, of potential use in shaping planning by medical physics 1. Ubiquitous in personal experience e- personal tricorders 2. Power, readout and internal processing of neural and other implants 3. Localized drug delivery and activation 4. Resolving of deep, even transcranial, 200 micron vessels 5. Medical physicists opportunities

6 Innovations in newer current systems 1. Software beam formers 2. Shear wave speed imaging (elastography) 3. 4D color flow contrast and non-contrast imaging 4. Aberration correction D Wildes, AIUM 05

7 Synthetic aperture imaging Adapted from Cobbold, Foundations of Biomedical Ultrasound, Oxford Press, 2007, p 34. JA Jensen, et al., Ultrasonics, Suppl. 2006, pp e5ff.

8 Aberration correction Lindsey & Smith, Pitch-catch phase aberration correction of multiple isoplanatic patches for 3- D transcranial US, IEEE TUFFC, 60, 463, 2013 (Ultras. Imaging, Jan: 35-54, 2014). Beam pretty good up to rms phase noise of 0.1 τ M. W. Urban

9 Perspective from the more distant future Smith, S.W., et al., IEEE Trans,. Ultras. Ferroel. Freq. Contr., 38, 1991, Lemmerhirt, D., et al., A 32 x 32 capacitive micromachined ultrasonic transducer array manufactured in standard CMOS. IEEE Trans.Ultras, Ferroel. Freq. Contr., 59, , 2012 I. High end medical future a. Full 2D arrays evolution is here b. Aberration correction c. Super resolution II. High performance US simple in the future, thus ubiquitous III. Medical physicists can serve broad spectrum of society electronic 4D imaging

10 Ultrasound 1.0 ZF Lu, PhD 1. System performance Introduction Ultrasound phantoms Ultrasound image quality metrics 2. System implementation Efficacy and sensitivity of current ultrasound QA/QC 3. Testing paradigm Survey of voluntary ultrasound accreditation programs Survey of available standards for diagnostic ultrasound

11 Various Levels of QC Testing Testing Time and Methods Testing Frequency Testing Personnel Level 1 Quick check; no special tool needed; Daily or weekly or monthly By ultrasound system users and overseen by medical physicists Level 2 Quick QC tests with a simple phantom; Quarterly or semi-annually By ultrasound system users and overseen by medical physicists Level 3 Comprehensive QC tests with phantoms; Annual or every two years By medical physicists 2013 MFMER slide-11

12 Ultrasound Phantoms Tissue-mimicking Speed of sound propagation Attenuation coefficient Backscatter coefficient (echogenicity) Built-in targets Ultrasound elastography properties Water-based versus rubber-based Caution about phantom desiccation Caution about sound speed effect 2013 MFMER slide-12

13 More Ultrasound Phantoms ATS Gammex/RMI E Madsen, AIUM DM King, et al, Phys. Med. Biol. 55, N557-N570, MFMER slide-13

14 Current Image Quality Metrics B-Mode - Image geometry - Maximum depth of penetration (system sensitivity) - Image uniformity and artifact survey - Ring down - Lesion detectability with a spherical lesion phantom - Spatial resolution (axial, lateral, elevational) - Contrast resolution Common approaches are mainly visual & qualitative 2013 MFMER slide-14

15 Current Image Quality Metrics Doppler Ultrasound - Doppler signal sensitivity - Doppler angle accuracy - Color display and gray-scale image congruency - Flow read-out accuracy Scanner and PACS Displays Common approaches are mainly visual & qualitative 2013 MFMER slide-15

16 1. System performance Introduction Ultrasound phantoms Ultrasound image quality metrics 2. System implementation Efficacy and sensitivity of current ultrasound QA/QC Reports in literature draw mixed conclusions 3. Testing paradigm Survey of voluntary ultrasound accreditation programs AIUM, ACR Survey of available standards for diagnostic ultrasound

17 Role of physics in future ultrasound practices Performance testing Image quality metrics and assessment methodology Further development of quantitative software analysis tools and test protocols is needed Traditional performance metrics New performance metrics (elastography, QUS) Validation of methods Signal accuracy/sensitivity and precision Automated or semi-automated tools repeatability Real-time workflow Wide availability Phantom vendors 2013 MFMER slide-17

18 Role of physics in future ultrasound practices Performance testing Image quality metrics and assessment methodology Task-specific performance measures based on detection or characterization of phantom targets more integrated and clinically-relevant quality measures Contrast-detail analysis Target signal-to-noise ratio Resolution integral 2013 MFMER slide-18

19 Role of physics in future ultrasound practices Performance testing Image quality metrics and assessment methodology: Task-specific measures Phantoms and targets Anechoic and echogenic cylinders Anechoic spheres Observers Human (ROC, 2AFC tasks) Computer (matched filter, model observers, target segmentation)? 2013 MFMER slide-19

20 Role of physics in future ultrasound practices Performance testing Image quality metrics and assessment methodology: Task-specific measures Challenges include Statistical requirements Many independent target images Assumptions about the imaging system (Linear? Shift-invariant? Gaussian noise?) Testing the system, not the operator Phantoms that can accommodate all modern imaging equipment, and model a wide variety of clinical applications Testing paradigms reflecting wider variety of clinical tasks 2013 MFMER slide-20

21 Role of physics in future ultrasound practices Performance testing Testing scenarios Why do we test? Purpose Frequency Methods Personnel Technology assessment / Pre-purchase testing Ad hoc Most comprehensive, objective, quantititative, clinically-relevent, robust vs basic control settings + acceptance tests Physicist & physics assistant Acceptance testing Re/application for practice accreditation At clinical implementation As specified by accrediting body Objective, traditional performance measures (DOP, Uni, Geo, Spatial res, Physics assistant Contrast, Display, etc) + connectivity & physicist As specified by accrediting body (subset of acceptance tests) Physics assistant with physicist support and oversight Routine QC (Testing levels 1 & 2) Daily On-board vendor diagnostics - Auto data logging, problem alert - Practice specification of alert levels Service group to respond to alerts Comprehensive physics survey (Testing level 3) Same as for accred., or as appropriate for the specific US system Same as acceptance or accreditation testing Physics assistant with physicist support and oversight 2013 MFMER slide-21

22 Role of physics in future ultrasound practices Performance testing Testing scenarios Technology assessment / pre-purchase testing Most comprehensive level of system evaluation Extensive physics/phantom testing, with quantitative methods, even at expense of efficiency Volunteer imaging, categorical data Patient imaging, categorical data Connectivity and workflow Usability, service-ability, etc 2013 MFMER slide-22

23 Role of physics in future ultrasound practices Performance testing Testing scenarios Accreditation and regulatory compliance Acceptance testing Comprehensive physics survey Routine quality control Challenge: clinically-relevant performance benchmarks What defines acceptable and unacceptable performance? What quality and risk factors should be considered? 2013 MFMER slide-23

24 Role of physics in future ultrasound practices Optimization of image quality & exam protocols Quantitative measurements Limited vendor guidance re use of measurement tools Normalize measurement calibration across ultrasound system models, probes, and vendors 2013 MFMER slide-24

25 Role of physics in future ultrasound practices Optimization of image quality & exam protocols Standardized dx exam protocols & imaging presets Sharing clinical diagnostic work across geographicallydistributed practices, and A variety of US systems and vendors Vendors: remote system management tools? 2013 MFMER slide-25

26 Role of physics in future ultrasound practices Clinical innovation Assessment and implementation of new ultrasound technologies Developing initial exam protocols, imaging presets, and measurement protocols, for new modes and features Greater use of image measurements & metadata Practice resource utilization and management Quality improvement of imaging presets Enhanced exam interpretation modes and clinical result sets Improved practice efficiency General improvement of overall practice quality & safety, not just image quality 2013 MFMER slide-26

27 Role of physics in future ultrasound practices Education Physicians, sonographers/technologists residents, medical students, patients Physics and technology of ultrasound imaging systems Board certification Sub/specialty certifications Practical knowledge to improve the quality of exam interpretations What knowledge is really needed by practitioners? 2013 MFMER slide-27

28 Clinical implementation Partner with the clinical practice The problem: An enormous amount of clinical equipment, wide range of technology sophistication, implemented across multiple departments with different practice workflows, inconsistent training and education, increasing financial pressures, and limited technical support historically 2013 MFMER slide-28

29 Clinical implementation Build and lead a technical support team The team: Physician practice leader Practice manager Sonographer/tech manager, lead, educator Service engineer Physics assistant Physicist Vendor product team (key partners, not leaders) Performance testing Optimization of image quality and exam protocols Clinical innovation in all aspects of practice Education 2013 MFMER slide-29

30 Clinical implementation Continuous quality improvement Evidence-based performance testing program, that emphasizes actual value (risk/cost) Expand the technology assessment protocol to address new functionality Assess utility for annual performance surveys and routine QC on a small scale Optimize routine QC methods Optimize the routine testing program in response to technology level, clinical application, prior data, & technology advancement What tests, methods, personnel, and frequency optimize actual value for the clinical practice? GE Healthcare 2013 MFMER slide-30

31 Conclusion Ultrasound use is expected to grow rapidly Ultrasound imaging systems are undergoing rapid development and innovation New sources of image contrast Improved quantitation Improved metadata and practice analytics Bracco 2013 MFMER slide-31

32 Conclusion Medical physicists working in partnership with clinical practices will be critical to optimizing practice quality, safety & value Performance testing Optimization of image quality and exam protocols Clinical innovation in all aspects of practice Education Demonstrating the value of physics services will become increasingly important 2013 MFMER slide-32